In the oil and gas industry, tongs are typically used to grip tubular members for connecting and disconnecting two tubular members. More particularly, a first type of tong (i.e., a power tong) rotates a first threaded tubular member, while a second type of tong (i.e., a backup tong) secures a second threaded tubular member against rotation. A single wellbore can have tubular members of varying diameters introduced therein. As the diameter increases, the torque required to achieve satisfactory makeup of a threaded connection may also increase. To achieve high make-up/break-out torque, the tong may use a plurality of jaws, which are fitted with dies, to provide adequate radial gripping force while avoiding deformation of the tubular member. The gripping force may be distributed more evenly circumferentially around the tubular member by increasing the number of jaws around the tubular member.
Conventional power tongs come in different types. One type includes a simple slotted rotary gear and retractable jaws that move radially by rotating the gear. Typically, this type has a limited range of torque due to a limited number of jaws in the tong. A second type includes a simple slotted rotary gear and pivoting jaws. The tubular members gripped by the tong can vary in diameter (e.g., due to industry standard tolerances even between tubular members that are nominally the same diameter). This can result in the pivoting jaws gripping the tubular member in a slightly eccentric position, which can result in uneven loading and potentially deformation of the tubular member, especially in high-torque applications. A third type of power tong includes a rotary gear and retractable jaws that move radially by rotating the gear. The gear includes a first rotary gear segment in a body of the power tong, and a second rotary gear segment in a door of the power tong. When the second rotary gear segment is aligned with the door and a slot (or “throat”) in the body, the door can be opened, with the second rotary gear segment moving along with the door, thereby exposing the throat and allowing the tubular member to be inserted or removed laterally therethrough. This design ensures a generally uniform, centralized gripping of the tubular members. While this design is employed in the oilfield, having a segmented rotary gear complicates the operation of the tongs because it requires precisely positioning the rotary gear with respect to the tong body, so as to allow the door with the second rotary gear segment to swing open, away from the first rotary gear segment, and expose the slot for lateral movement of the tubular member.